Men inspect a bus following an explosion on the street in Potiskum, Nigeria. Tuesday, Feb. 24, 2015 . A man forced his way onto a bus at a crowded bus station and detonated explosives that killed 12 people and injured 20 in northeast Nigeria, according to the bus driver and hospital records. The attack in Potiskum comes two days after a girl who looked about 10 years old detonated explosives that killed herself and four others at a market in the same town. (AP Photo/Adamu Adamu )
(The Associated Press)

A man inspects a bus following an explosion on the street in Potiskum, Nigeria. Tuesday, Feb. 24, 2015 . A man forced his way onto a bus at a crowded bus station and detonated explosives that killed 12 people and injured 20 in northeast Nigeria, according to the bus driver and hospital records. The attack in Potiskum comes two days after a girl who looked about 10 years old detonated explosives that killed herself and four others at a market in the same town. (AP Photo/Adamu Adamu )
(The Associated Press)

Injured people from a bus explosion receive treatment at a local hospital in Potiskum, Nigeria. Tuesday, Feb. 24, 2015 . A man forced his way onto a bus at a crowded bus station and detonated explosives that killed 12 people and injured 20 in northeast Nigeria, according to the bus driver and hospital records. The attack in Potiskum comes two days after a girl who looked about 10 years old detonated explosives that killed herself and four others at a market in the same town. (AP Photo/Adamu Adamu )
(The Associated Press)

POTISKUM, Nigeria – A witness and hospital records say a man forced his way onto a bus at a crowded bus station and detonated explosives, killing 12 people and injuring 20 in the northeastern Nigerian town of Potiskum.

There was no immediate claim of responsibility for Tuesday's blast but it bore the signs of similar attacks by Nigeria's home-grown Boko Haram Islamic extremist group.

Bus driver Adamu Isa said the man forced himself onto the bus and blew himself up. Hospital records show 12 people died and 20 were injured.

In the same town on Sunday a girl who looked about 10 carried explosives that detonated that killing herself and four others at a market.

Thousands of people have been killed in the 5-year-old uprising to enforce strict Islamic law in Nigeria.